syzkaller is an automated fuzzer that generates kernel activity and uses code coverage to find bugs in operating-system kernels. It is used by kernel developers and security researchers to test Linux and other supported kernels for vulnerabilities and failures. The catalogue add-ons help coding agents operate or use syzkaller.
Borrowing it
Nothing to install: this file belongs to google/syzkaller. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/google/syzkaller/master/.agents/skills/syzlang-vm-testing/SKILL.mdgit clone --depth 1 https://github.com/google/syzkallerWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/google/syzkaller/syzlang-vm-testing)<a href="https://agentmods.dev/skills/google/syzkaller/syzlang-vm-testing"><img src="https://agentmods.dev/badge/skills/google/syzkaller/syzlang-vm-testing/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/google/syzkaller/syzlang-vm-testing"><img src="https://agentmods.dev/badge/skills/google/syzkaller/syzlang-vm-testing.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00055 | $0.01316 |
| Opus 5.5 | $0.00022 | $0.00526 |
| Sonnet 5.5 | $0.00011 | $0.00263 |
| Haiku 4.5 | $0.00006 | $0.00132 |
Grade A, and why
syzlang-vm-testing scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 101 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Syzlang & Seed Program QEMU VM Verification
Use this skill to verify new or updated Linux syscall descriptions (sys/linux/*.txt), executor
setup (executor/common_linux.h), and seed programs (sys/linux/test/*) inside a QEMU VM.
For general syzlang description and seed authoring rules (and host-side parsing tests), see
sys/GEMINI.md.
1. Obtaining the VM Disk Image and Kernel
-
Userspace Disk Image (Buildroot): If no disk image is available locally, download and decompress the standard syzkaller buildroot image from
https://storage.googleapis.com/syzkaller/images/buildroot-amd64-2025.05.gz. -
Kernel Image (
bzImageandvmlinux):- If the user provided a Linux kernel build directory or
bzImagepath, use it. - Otherwise, visit
https://syzkaller.appspot.com/upstream/manager/ci-qemu-upstream, download the latestkernel image(bzImage) andvmlinux(if needed for coverage symbolization), and decompress them.
- If the user provided a Linux kernel build directory or
2. Running Seed Programs via syz-manager -mode run-tests
Build syz-manager and syz-executor:
CI=true ./tools/syz-env make manager executor
Create a minimal syz-manager config (e.g., /tmp/runtest.cfg):
{
"name": "runtest",
"target": "linux/amd64",
"http": "127.0.0.1:0",
"workdir": "/tmp/syz-runtest-workdir",
"image": "/tmp/buildroot-amd64.img",
"syzkaller": ".",
"sandbox": "none",
"procs": 1,
"type": "qemu",
"vm": {
"count": 1,
"kernel": "/tmp/bzImage",
"cmdline": "root=/dev/sda1",
"cpu": 2,
"mem": 2048
}
}
- KVM vs TCG: By default on
linux/amd64, syzkaller passes-enable-kvm -cpu host,migratable=offto QEMU. If KVM (/dev/kvm) is available on the host, always use it. If KVM is not available, configure TCG invm.qemu_args(e.g.,"qemu_args": "-machine q35 -accel tcg -cpu max") and be very patient, as booting an instrumented kernel under software emulation takes several minutes. - Sandbox: If the seed program targets syscalls fuzzed under
"sandbox": "namespace"in production, also test with"sandbox": "namespace"to verify that devices or sockets created ininit_network from child network namespaces.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 3d ago First seen · 101 lines · 55 tokens per session scan A 871e67521b81
syzlang-vm-testing is a skill published in the GitHub repository google/syzkaller (6,383 stars, last pushed today), licensed Apache-2.0. It adds 55 tokens to every session and 1,316 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-10-26.
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